OPIOID ANTAGONIST AFFECTS BEHAVIORAL-EFFECTS OF EXPOSURE IN-VIVO

This study tested the hypothesis that endogenous opioids are involved in the extinction of phobic fear through exposure in vivo. Forty-eight spider phobics participated in a 2-hr therapist-directed exposure in vivo treatment. Sixteen Ss were assigned to placebo, 16 to a low dose of naltrexone, and 16 to a high dose of naltrexone. Before interventio n, after treatment, and at a 1-wk follow-up test, self-report, physiol ogical, and behavioral measures of phobic fear were completed. At 1-wk follow-up, naltrexone was significantly related, in a dose-dependent way, to a greater relapse on avoidance measures but not on emotional, cognitive, and physiological measures. Endogenous opioids may be speci fically involved in the extinction of avoidance behavior but not in th e extinction of all aspects of phobic fear.